The present invention relates to a plasma processing apparatus and in particular to a plasma processing apparatus suitable for formation of various sorts of films, etching processing therefor, etc., effected in semiconductor element fabrication, etc.
Recently, down sizing and higher density integration of semiconductor elements have continued to progress. A microwave plasma processing apparatus can be cited as a processing apparatus suitable for such down sizing. A prior art microwave plasma processing apparatus described e.g. in Japanese Utility Model Publication Laid-Open No. 2-67632 is known. In this microwave plasma processing apparatus, a bell jar made of quartz is disposed in the upper part of a vacuum chamber, in which a sample table is disposed, a waveguide, at an end of which a magnetron is mounted, is disposed around the quartz bell jar, a coil for generating a magnetic field is disposed around the quartz bell jar through the magnetic waveguide, a high frequency power supply is connected with the sample table, and a movable ground plate is disposed around a sample placed on the sample table. The apparatus described above operates as follows. Gas is introduced into the vacuum chamber through a processing gas introducing tube. Microwaves from the magnetron are injected in the quartz bell jar and at the same time a magnetic field is generated in the quartz bell jar. In this way, plasma is produced by the effect of the microwaves and the magnetic field in the quartz bell jar, and a bias voltage is produced by applying a high frequency voltage to the sample table. At this time, the height of the ground plate is regulated so that a potential distribution is made uniform.
In the prior art technique described above, no attention was paid to metal contamination by the ground plate, and there was a problem that the ground plate was sputtered by ions in the plasma generated in the quartz bell jar and sputter particles were scattered in the vacuum chamber to contaminate the sample.
The object of the present invention is to provide a plasma processing apparatus capable of effect stable plasma processing without any metal contamination.